Loess in Northern Iran: Key for Understanding Quaternary Climate Changes in Central Asia and Relation to Monsoonal Asia

Loess-paleosol sequences from northern Iran provide unique sedimentary archives for reconstructing the long-term climate change history in western arid central Asia, and for decoupling the role of interactions between the Westerlies and Asian monsoon in determining the spatiotemporal patterns of climate changes across the mid-latitude Asia. Here we show that the Pleistocene loess-paleosol sequences in arid central Asia are characterized by development of paleosols during interglacial periods and accumulation of loess during glacial periods. Multi-proxy indices records reveal an overall consistent wet-dry climate change history between the westerlies Asian and the northern Monsoonal Asia on orbital timescale since at least ۲.۴ Ma. Novel paleo-precipitation seasonality records, using the range of stable oxygen isotope compositions within single shell of land snails, provide evidence that the late Quaternary precipitations were concentrated in winter seasons in westerlies Asia and in summer seasons in the Monsoonal Asia, respectively. Integrating with modelling evidence suggest distinct seasonal characteristics of interactions between the westerlies and Asian monsoon during the late Quaternary period, which had a synergistic impact on glacial-interglacial climate changes in mid-latitude Asia.

کلیدواژه ها:

Quaternary Loess ، North Iran ، Arid central Asia ، tectonic and orbital time scale